NMR Spectroscopic Study of Reaction Kinetics in Mixtures of Formaldehyde, Water, and Butynediol

Butynediol is an important intermediate in the chemical industry and is produced from acetylene and aqueous formaldehyde. Mixtures of formaldehyde + water + butynediol are complex reacting multicomponent systems in which oligomerization reactions of formaldehyde with both water and butynediol occur. The chemical equilibria of the reactions of formaldehyde with butynediol were studied recently by quantitative NMR spectroscopy (Berje et al., DOI: 10.1002/AIC.15788). The present work complements this by a kinetic study of these reactions. Aqueous formaldehyde solutions were diluted with aqueous butynediol solutions, and the kinetic response was monitored by ¹H NMR spectroscopy. Most of the experiments were carried out in NMR sample tubes; additional experiments were carried out with a micromixer NMR probe to extend the studied range to kinetics with time constants well below 1 min. The new reaction kinetic data cover temperatures between 293.15 and 328.15 K and pH values between 3 and 6. A reaction kinetic model was developed based on the equilibrium model from the previous study, and the reaction kinetic constants were determined from the new data. Furthermore, new reaction kinetic data for the system formaldehyde + water were measured, which extend the available data on that system to faster kinetics. These new data confirm the mole fraction-based reaction kinetic model of Hahnenstein et al. (DOI: 10.1021/ie00041a003).